Add arm64 compatibility

[Scout22]

I'm currently using the cust library in one of my projects, but I'm running into an issue where the library is not compatible with the arm64 architecture. This is causing build failures in my CI/CD pipeline when targeting arm64 platforms.
I understand that the library may have been primarily developed and tested on x86 architectures. However, as the use of arm64-based systems (emdedded device) continues to grow, it would be extremely helpful if the cust library could add support for these architectures.